1. Field of the Invention:
The invention relates in general to gas-insulated transmission lines and in particular to a gas-insulated transmission line having a corrugated outer conductor and a particle trap to sheath movable contact.
2. Description of the Prior Art:
Compressed gas-insulated transmission lines typically comprise a hollow, cylindrical outer sheath, an inner conductor disposed within, but spaced apart from, the outer sheath, a plurality of insulating spacers which support the conductor in the sheath, and a compressed gas such as sulphur hexafluoride or the like in the sheath to electrically insulate the conductor from the sheath or outer conductor.
One problem occurring in the use of gas-insulated transmission lines concerns the mobile conducting or semiconducting particle. These particles can cause problems in that they may lower the dielectric strength of the insulating gas and may initiate flashover and breakdown of the gas as they travel between the outer sheath and the inner conductor. Trump, in U.S. Pat. No. 3,515,939, discloses the means for deactivating and eliminating the deleterious effects of such conducting particles. In that patent, there is described the use of electrodes placed within the outer sheath to create low field regions which trap and deactivate the particles. The low field regions are created by keeping the particle trap electrode at the same potential as that of the outer sheath or outer conductor by means of a particle trap to sheath contact.
A recent development proposes to use corrugated aluminum for the outer conductor instead of the smooth aluminum cylindrical outer sheath. With such a corrugated outer conductor, a standard particle trap to sheath contact is not suitable to keep the particle trap in contact with the corrugated outer conductor and thereby at the same electrical potential because of the large variation between the inside diameter of the sheath and the outside diameter of the particle trap assembly due to the peaks and valleys of the sheath corrugations. A good reliable electrical connection between the particle trapping means and the outer corrugated conductor is disclosed in concurrently filed copending U.S. patent application Ser. No. 439,246, entitled "Particle Trap To Sheath Contact For A Gas-Insulated Transmission Line Having A Corrugated Outer Conductor" by W. H. Fischer, K. H. Yoon and A. H. Cookson and assigned to the same assignee as the present invention. While the electrical conductor contact means disclosed in this patent application provides a contact suitable for corrugated outer conductors having moderate slopes to the corrugations, it is possible that the contact means will bind up upon insertion of the insulator/particle trap/inner conductor assembly into a corrugated outer conductor having steep slopes to the corrugations. The present application discloses a contact means providing the same excellent electrical contact having the additional desirable feature of not binding for any slope of the corrugations less than vertical.